Most if not all of the later cars only have one sensor on the front right and one on the right rear. The theory being that they all will wear evenly which has turned out to be a joke. I get more and more of these that come in that have worn metal to metal because the inner pad on the side with no sensor has worn to nothing while the outer pad or the pad with the sensor may have 50% left. Just more of MBZ being cheap and cutting corners or securing more work. Either way you slice it, it's bad engineering.